The present chapter begins with the notion of function as found in the Begriffsschrift of 1879 and some related questions (6.1–6.3). The distinction function-argument is first considered from the point of view of its being preferred by Frege to the traditional subject-predicate (6.1). Frege's intention is to introduce a symbolism for relational propositions, which satisfies an old logical desideratum (6.11). In this context, there is occasion to mention Frege's relation with a member of Brentano's school, A. Marty (6.2). Finally, the notion of function in BG is presented (6.3).